Heat the butter or oil in a large skillet or wok over medium heat. Add the chicken and cook, stirring frequently, for 2-3 minutes until it is slightly opaque.
Add the garlic, ginger, scallions, celery, and pepper. Continue to cook, stirring frequently, until the chicken is cooked through.
Add the tamari, vinegar, and basil. Turn off the heat, stir, and let sit for 2-3 minutes. Season with chili powder to taste and serve.